Jupiter, the fifth planet from the Sun, is the largest planet in our solar system, so massive that it could fit more than 1,300 Earths inside it and is more than twice as massive as all the other planets combined. It is a gas giant composed mainly of hydrogen and helium, with no solid surface, and is known for its fast rotation—completing a day in just about 10 hours—which gives it a noticeable bulge at the equator. Jupiter’s atmosphere is famous for its colorful cloud bands and the Great Red Spot, a gigantic storm larger than Earth that has been raging for at least 350 years. It has a powerful magnetic field, the strongest of any planet, and a thin ring system. Jupiter is orbited by at least 95 moons, including the four large Galilean moons—Io, Europa, Ganymede, and Callisto—discovered by Galileo Galilei in 1610. These moons are worlds of their own: Europa may harbor a subsurface ocean that could support life, Io is the most volcanically active body in the solar system, Ganymede is the largest moon in the solar system, and Callisto is heavily cratered and ancient. Jupiter plays a crucial role in the solar system’s stability, its immense gravity deflecting or capturing many comets and asteroids that might otherwise strike the inner planets. Missions like Pioneer, Voyager, Galileo, and currently Juno have revealed much about its atmosphere, magnetic field, and moons, but many mysteries remain. Jupiter is not just a planet—it’s like a miniature solar system, an enormous and dynamic world whose influence reaches far beyond its own orbit.